Reciprocating stirling cycle engine with dual wave cam drive



D. A. KELLY Oct. 29; 1968 RECIPROCATING STIRLING CYCLE ENGINE WITH DUAL WAVE CAM DRIVE 5 Sheets-Sheet 1 Filed April 10, 1967 FIG 2 6 22 l8a In 21 METAL; 1c F/LAME/VT INVENTOR. final/aw RECIPROCATING STIRLING CYCLE ENGINE WITH DUAL WAVE CAM DRIVE fin l/ 25g Oct. 29, 1968 D. A. KELLY 3,407,593

RECIPROCATING STIRLING CYCLE ENGINE WITH DUAL WAVE CAM DRIVE Filed April 10, 1967 5 Sheets-Sheet 5 Jul/0% Oct. 29, 1968 KELLY 3,407,593

RECIPROCATING STIRLING CYCLE ENGINE WITH'DUAL WAVE CAM DRIVE Filed April 10, 1967 5 SheetsSheet 4 INVENTOR; I

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RE IPROCATING STIRLING CYCLE ENGINE WITH DUAL WAVE CAM DRIVE Filed April 10, 1967 5 Sheets-Sheet 5 IN V EN TOR.

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United States Patent 3,407,593 RECIPROCATING STIRLING CYCLE ENGINE WITH DUAL WAVE CAM DRIVE Donald A. Kelly, 58-06 69th Place, Maspeth, NY. 11378 Filed Apr. 10, 1967, Ser. No. 634,409 14 Claims. (Cl. 60-24) ABSTRACT OF THE DISCLOSURE A Stirling cycle engine having two wave cams on a common shaft and two coaxial pistons connected to sa1d wave cams which reciprocate within two cylinders; said wave cam having a cam track slidably associated with sa1d pistons; said pistons being one-half stroke out of phase.

This invention relates to a simplified reciprocating Stirling cycle engine in which the two conventional pistons are coaxially arranged with two wave cams connected to them. The major difference between the conventional reciprocating designs and this arrangement is that wave cams are utilized to reciprocate with the pistons. The application of wave cams is viewed as a means of simpl fy ng construction and producing a compact engine. The friction level at the cam track and rollers is minimized by the use of needle bearings revolving on the roller pins. In addition to reducing the number of parts such as rods and linkages and the wear associated with these, the application of wave cams affords a simple means of assembly and phasing adjustment between the Stirling piston pairs. S1nce a single wave cam is used the motion ach1eved 1s snmlar to a swash plate drive except that uniform motion results. Both wave cams have a helix angle ofabout 45 degrees for optimum rotation of the drive shaft without unduly high friction at the rollers. Unlike the twin-wave cam and multiple piston types previously disclosed the torque output is not doubled due to two power strokes per shaft revolution in this design. It should be noted that the single wave cam allows the pistons to fully traverse in one direction within the cylinders for 180 degrees of shaft rotation, which is identical to the operation of the conventional reciprocating Stirling cycle engine. When the cams are placed 90 degrees out of phase at the shaft, the two pistons are one-half stroke out of phase which is required for keying and proper operation of the cycle. Both pistons must be restrained from rotation in order to elfectively translate within the cylinders and small roller bearings are provided within the cylinder to reduce rolling friction and guide the pistons.

The classic Stirling closed cycle engine is basically an externally heated engine in which a constant volume of gas is alternately heated and cooled to produce the half power stroke and half pull stroke on the power piston. Various types of Stirling cycle engines are known, such as the conventional dual coaxial reciprocating engine now in use, sideby-side piston types and L or V types. The currently operating dual-coaxial piston engine is pressurized and operates at good efficiencies, but due to its configuration is hampered by an excessive number of rods and linkages. This complex linkage assembly is a drawback to the simple gauging of multiple cylinders to achieve efficient, high power-to-volume/weight Stirling engines.

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The present unique design allows the classic Stirling cycle pistons to be simply phase connected in a readily serviced compact arrangement. The design circumvents the complex linkage required by the current co-axial engine, by the application of the two wave cams on a common drive shaft. It should be realized that the displacer piston receives energy for reciprocation from its wave cam, while the power piston transmits thrust to its wave cam to produce the torque at the common drive shaft, and this functioning is similar to the compressor and power stages of a standard open cycle gas turbine. In this arrangement the displacer piston strokes need not be the same as that of the power piston since each piston has its own wave cam and therefore each displacement stroke may be suited to the volumetric arrangement required.

In this engine design no special attempt is made to approcah true isothermal operation by the addition of interlocking fins or saturation filament at both ends of the displacer cylinder, although such methods may be employed if the specific engine application dictates that operating efliciency would be enhanced. The acceptance of the expansion and compression function closer to adiabatic than isothermal is viewed as characteristic of general Stirling cycle configuration and it would appear that improved efliciencies will result by improved regeneration techniques and volumetric proportions.

A means of aiding thermal operating efiiciency in this design is the splitting of the displacer housing and the isolation of the two halves into hot and cold sections to achieve a maximum delta temperature. The heating of the hot section would be accomplished by direct flame on the cylinder wall or through a conductive metal volume which would serve to store heat. The cooling of the cold section would be accomplished by placing continuous liquid cooling tubes in direct contact with the cylinder walls or possibly embedded within the Walls of the cold section. This arrangement, although not as theoretically efiicient as other systems is within the realm of producibility and economical feasibility.

This cycle can be inverted to operate as refrigeration equipment when coupled to a suitable power source such as an electric motor. When the machine is operated in this manner the normally hot side will become cold and the normally cold side will become hot. A distribution and heat sink arrangement must be made to utilize the cooling produced.

An alternate arrangement of the basic engine would consist of a relatively large twin semi-circular displacer piston halves and a single wave cam as a displacer section with small twin pistons and single wave cam, as a power section. The single wave displacer cam would reciprocate the displacer piston halves in opposite directions within the displacer cylinder to form the standard hot and cold displacer volumes. The displacer piston halves contain cavities sufficient to allow for the clear revolution of the cam within the piston halves. The piston halves are restrained from tending to revolve with the rotating cams by the divider plate. The divider plate separates the two displacer piston halves and seals ofi? the two displacer cavity halves. Since the semi-cricular displacer piston halves are located at opposite ends of the single wave cam and therefore move in opposite directions, their thrusts cancel out so that running roughness and vibrations are minimized. The twin displacer halves would be fitted with ball bearings to suspend the pistons from contact with the displacer cylinder walls.

The twin power pistons drive the power cam which is 90 degrees out of phase with the displacer cam. Four power pistons may be utilized to provide double the power pulses on the cam track for more uniform power flow. The expanding and contracting gas flow would be conducted through multiple ports between the displacer and power sections.

It is most desirable to simplify Stirling engine design in order to simplify manufacture, operation, servicing and maintaining, while achieving a maximum power-tovolume output.

It is an object of the invention to create a simple Stirling cycle engine while maintaining all the operating characteristics of the cycle.

It is a further object of the invention to create a simplified Stirling cycle engine with independent strokes for each piston and ease of phase adjustment by utilizing two wave cams on a common drive shaft.

It is an object of the invention to create a long-lived, maintenance-eased Stirling engine without the requirement of a high pressure seal at the output shaft.

It is an object of the invention to simplify regeneration techniques by adopting multiple, long-path, small diameter regenerator bores within the displacer piston or pistons.

It is a final object of the invention to produce a lowcost engine or refrigeration machine that is easy to assemble, disassemble and service,

Other features will become apparent from the following description of the engine design. It should be understood that variations may be made in the detail design without departing from the spirit and scope of the invention.

Referring to the drawings in detail,

FIGURE 1 is a front section view through the displacer cylinder section.

FIGURE 2 is a side section view through the engine.

FIGURE 3 is a front section view through an alternate rotary power section.

FIGURE 4 is a side section view through an alternate engine arrangement.

FIGURE 5 is a front section view through an alternate displacer section.

FIGURE 6 is a side section view through an alternate half-rotary engine.

FIGURE 7 is a pictorial exploded view of the pre ferred engine operating components.

FIGURE 8 is a pictorial exploded view of the alternate engine operating components.

Referring to FIGURE 1 and 2, the displacer cylinder 1 is made up of three parts, a hot cylinder 1a, a cold cylinder 1b, and an insulation sleeve 1c, which form an integral, inseparable displacer cylinder.

The end plates 2 and 3 are secured to the displacer cylinder 1 to form a sealed displacer housing. The screws 31 fasten the end plates 2 and 3 to the displacer cylinder 1 with the gasket 34 making the displacer housing gastight. The cylindrical displacer piston 4 reciprocates within the housing and is suspended with small clearance from the inside diameter by the ball bearings 10 and pins 42. The sealing disc 4a provides a means of assembly and seals the displacer gas volume from entering the displacer cavity 9. The screws 41 secure the sealing disc to the cavity diameter with suitable sealing compound providing a gastight pressure seal. The two guide segments 23 are fastened to the inside diameter of the displacer housing by the screws 31. The guide segments 23 prevent the displacer piston from revolving by coacting with the displacer fiat 4b and the ball bearings 10.

The displacer wave cam 5 is secured to the drive shaft 13 with the cam track 6 forming the displacement means for the roller bearings 7 and pins 8. The rollers and pins are secured to the inside diameter wall of the cavity 9 which provides displacement clearance for the piston about the wave cam 5, during its excursions. Small diameter regenerator bores 11 are located equally spaced around the end surface of the displacer piston 4 and run through it parallel to the drive shaft axis.

The roller bearings 12 support the drive shaft 13 within the end plates 2 and 3.

The power wave cam 14 is secured to the drive shaft 13 with the cam track 15 forming the displacement means for the roller bearing 24 and pin 25. The roller and pin are secured to the inside diameter wall of the power piston cavity 16. The cavity 16 is the open portion of the power piston 17 in which the power cam 14 rotates and which provides displacement clearance for the piston during its power excursions.

The power cylinder 18 to which the end plates 19 and 20 are fastened form the sealed power cylinder housing with the gasket 49 making the power cylinder housing gastight. The screws 32 and 33 fasten the end plates 19 and 20 to the power cylinder 18. The long rectangular key 21 is secured to a slot 18a within the inside wall of the power cylinder and fits in a corresponding slot 17a within the power piston 17, which prevents the power piston from revolving.

The power piston rings 22 are fitted to the piston to seal the gas within the working volume.

The front flange 28 contains the shaft seal 29 in contact with the shaft 13 and the front plate 19. The screws 30 secure the flange 28 to the front plate 19. The sealing rings 43 are required to prevent the working gas from escaping by the pistons 4 and 17 at the shaft 13. These rings will be subjected to severe conditions since they must seal against both rotation and reciprocation at the shaft, and will likely be made of Viton. The shaft 13 will require a finish of 16V or better to prevent undue wear on the seals.

The thrust collars 44 secured to the drive shaft 13 and transmit the axial piston thrust to the roller bearings 12.

The multiple ports 20a in end plate 20 and 23a in end plate 2 must be equal in size and line up in order to trans mit the ebb and flow of the internal working gas, acting on the power piston 17.

In the alternate arrangement the same displacer cylinder 1 and housing components will be required as in the first design. A divider plate 45 will split the displacer housing longitudinally at the horizontal centerline and be secured to the inside cylinder walls with the screws 31. The bore 47, at the exact longitudinal center of the divider plate provides clearance for the drive shaft 13. An opening 48 in the center of the divider plate 45, provides clearance for the rotation of the displacer wave cam 5.

The displacer pistons 4 are identical halves and slide in contact with the two faces of the divider plate 45. The displacer wave cam 5 is secured to the drive shaft 13 with the cam track 6 forming the displacement means for the roller bearings 7 and pins 8. The roller bearings and pins are secured to the inside diameter wall of the piston cavity 9.

Since the piston halves 4 are connected to diametrically opposite ends of the displacer wave cam 5 their dis-placement is equal and opposite to each other. The piston halves are restrained from a tendency to rotate by their contact with the divider plate 45. The contact with the divider plate is maintained by the bearings 10 and ins 42 located on the periphery of the displacer halves, while also providing the small clearance necessary between the piston halves and the inside diameter of the displacer housing.

The seals 46 located across the ends and sides of the flats of the displacer halves serve to seal the working gas from entering the displacer cavity 9. Small diameter regenerator bores ll are located equally spaced around the end surface of the displacer piston 4 and run through it parallel to the drive shaft axis. The roller bearings 12 support the drive shaft 13 within the end plates 2 and 3. The thrust collars 44 secured to the drive shaft 13 and transmit the axial piston thrusts to the roller bearings 12. The power section consists of the same components as in the first design, 18, 19, 20, 32 and 33 into which a cylindrical piston block 39 is retained. Two, four or more piston bores 38 contain the multiple power pistons 35. The power wave cam 14 is secured to the drive shaft 13 with the cam track 15 forming the thrust transmitting means from the roller bearings 36. The power cam 14 is placed about 90 degrees out of phase with the displacer cam 5 as required to key the cycle. The rollers and pins 36 and 37 are secured to the power pistons, which reciprocate within the power bores 38.

Additional thrust collars 44 secured to the drive shaft 13 transmit the axial piston thrusts to the bearings 12. The two bearings 12 are located within the end plates 19 and 20.

The end flange arrangement 28 is the same as the first design and includes parts 29, 30.

It may be possible to eliminate power cylinder components 18, 19, and 20, if the cylindrical piston block 39 is of sufficient strength to contain the high internal pressures developed within the power section.

The multiple ports a in the end plate 20 and 2a in the end plate 2, must be equal in size and line up with the power piston bores in order to transmit the ebb and flow of the internal working gas, acting on the power pistons 35. The piston rings 40 seal the working gas from escaping and assure power transmission to the power cam. AS is evident the number of transmitting ports 20a and 2a sets will be equal to the number of power pistons.

An alternate power section would consist of a rotor and sliding vane assembly eccentrically rotating in a cylindrical housing 50. The slotted rotor 51 would contain the shaped vanes 52 and 53 which interlock and slide to maintain contact and seal the crescent cavities within the rotary power section, housing 50. The vanes would be sealed gas pressure tight by the seals 54 and 55, which are held in contact with inside diameter walls by the springs 56 and 57, respectively. A valve disc 58-, is fastened to the drive shaft within the power cylindrical to isolate the hot gas flow from the cold, during the cycle.

The multiple ports 20a in the end plate 20 and 2a in the end plate 2 line up with the power housing cavities and with the ports of the valve disc 58. A key 59 secures the rotor 51 to the drive shaft 13. The end flange arrangement 28, 29, is the same as in the first design.

Various gauges will be required for the engine, but these are not shown nor described in detail since they are incidental to the overall engine designs. Gas filler valves will also be required and these are not shown since they may be placed at any convenient point in the engine housing.

An additional shaft extension may be required for driving an alternator and an electric starter drive. An electric starter system would be required, with an alternator recharging the battey through a voltage regulator. The battery would supply the current required by the starter as in a conventional system. No other accessories would be required with the possible exception of a liquid fuel pump.

An optional component for all the engine designs would be the addition of thin, flexible metallic strips 60, which serve to conduct heat uniformly throughout the heated displacement volume. For convenience in assembly the strips would be attached to the end plate 3.

What is claimed is:

1. In a reciprocating Stirling cycle engine having two coaxial pistons and a pressurized gaseous medium; the combination comprising two coaxial piston housings; a drive shaft rotatably mounted within said housing; two wave cam means mounted on said drive shaft for rotation therewith; guidance and bearing means within said two coaxial pistons for rolling association with said wave cam means; keying means within each of said piston housings for coaction with said two coaxial pistons; bearing means for said drive shaft rotatably mounted within said housing; sealing means within said two coaxial pistons for slidable association with said driveshaft.

2. The combination set forth in claim 1 including a sealing disc bonded to one end of one of said coaxial pistons.

3. The combination set forth in claim 1 including multiple small diameter regenerator bores axially disposed within one of said coaxial pistons; fine metallic filament dispersed within said multiple small diameter regenerator bores.

4. The combination set forth in claim 1 wherein one of said two coaxial pistons is provided with axially disposed bearing means.

5. The combination set forth in claim 1 including thin flexible metallic strips uniformly disposed at both ends of one of said two coaxial piston housings.

6. In a receprocating Stirling cycle engine having two semicircular piston halves; multiple small diameter pistons and a pressurized gaseous medium; the combination comprising two coaxial piston housings; a longitudinal divider plate within one of said two coaxial piston housings thereby forming two semi-circular elongate cavities within said piston housing; said longitudinal divider plate and said drive shaft being arranged in parallelism; a drive shaft rotatably mounted within said two coaxial piston housings; two wave cam means mounted on said driveshaft for rotation therewith; guidance and bearing means within said two semi-circular piston halves for rolling association with one of said wave cam means; guidance and bearing means on said multiple small pistons for rolling association with the other said wave cam means; bearing means for said drive shaft within said two coaxial piston housings; sealing means within said piston halves for slidable association with said longitudinal divider plate and one of said coaxial piston housing and the bores therein.

7. The combination set forth in claim 6 including rnul tiple small diameter regenerator bores axial disposed within said two semi-circular piston halves.

8. The combination set forth in claim 6 wherein the said two semi-circular piston halves are fitted with axial disposed ball bearing means.

9. The combination set forth in claim 6 including thin flexible metallic strips uniformly disposed at either or both ends of said two coaxial piston housings.

10. In a reciprocating Stirling cycle engine having two semi-circular piston halves and a pressurized gaseous medium, the combination comprising a displacer housing; a drive shaft rotatably mounted within said displacer housing; a wave cam means mounted on said drive shaft for rotation therewith; a longitudinal divider plate within said displacer housing thereby forming two semi-circular elongate cavities; said longitudinal divider plate and said drive shaft being arranged in parallelism; guidance and bearing means within said two semi-circular piston halves for rolling association with said Wave cam means; bearing means for said drive shaft within said displacer housing; sealing means within said two semi-circular piston halves for slidable association with said longitudinal divider plate; two ports disposed at one end of said displacer housing; a second cylindrical housing disposed coaxially with said displacer housing; a slotted rotor eccentrically located within said second cylindrical housing; a short bore in said slotted rotor; multiple movable and interlocking power vanes disposed within said slotted rotor; sealing means within said power vanes for slidable association within said cylindrical housing which line up with said two ports at one end of said displacer housing.

11. The combination set forth in claim 10 including multiple small diameter regenerator bores axially disposed within the said two semi-circular piston halves; fine metallic filament dispersed within said regenerator bores.

12. The combination set forth in claim 10 wherein the said multiple movable and interlocking power vanes are in independent of each other; spring loading means for said independent power vanes.

13. The combination set forth in claim 10 including a valve disc secured to the said drive shaft within the said displacer housing.

14. The combination set forth in claim 10 wherein said second cylindrical housing is fitted with a seal means in rotating association with said drive shaft.

References Cited UNITED STATES PATENTS Bleser 123-58 X Smith. v

Du Pre 60-24 X Korsgren 123-58 X Ciaccia- 92-178 10 CARROLL B. DORITY, IR., Primary Examiner. 

